Manual asymmetries in the kinematics of reach-to-grasp actions

Abstract

The purpose of this thesis was to investigate manual asymmetries in the reach-to-grasp movement based on two hypotheses: 1) manual asymmetries are resultant from asymmetries in the dorsal vision-for-action system; and 2) manual asymmetries are contingent on task difficulty. Participants grasped glasses of water under different visual-feedback conditions. Demand was manipulated by varying the level of the water contained in the glass. Hand asymmetries of the reach-to-grasp movement were studied through kinematic analyses. Visual feedback availability and task demand affected all kinematic measures. Manual asymmetries were found in peak velocity, movement time, and variability of maximum grip aperture. Consistent with reach-to-point literature, reach-to-grasp actions were faster and more accurate when performed with the right hand and when guided by the dorsal vision-for-action system. The results of the thesis provide support for a theory of left-hemisphere specialization for the visual control of actions.